Matrix metalloproteinases (MMPs) collectively degrade all extracellular matrix (ECM) proteins. MMP-9 has the strongest link to development of cardiac dysfunction. Aging is associated with increased MMP-9 expression in the left ventricle (LV) and reduced cardiac function. We investigated the effect of MMP-9 deletion on the cardiac ECM in aged mice. Based on label-free mass spectrometry analyses, MMP-9 dependent age-related changes were found in the mouse cardiac ECM proteome, suggesting MMP-9 as a possible therapeutic target for the aging patient